1. Field of the Invention
This invention relates to a method of manufacturing a spacer assembly used in a flat display device.
2. Description of the Related Art
A field emission display (FED), plasma display (PDP), etc. are known as modern flat display devices. A display that uses a surface-conduction electron source (hereinafter referred to as SED) is being developed as an FED of a kind.
This SED has a faceplate and a rear plate that are opposed to each other with a given gap between them. These plates have their respective peripheral edge portions jointed together by a rectangular frame-shaped sidewall, thus forming a vacuum envelope. Phosphor layers that glow in three colors are formed on the inner surface of the faceplate. Arranged on the inner surface of the rear plate are a number of emitters that correspond individually to pixels as electron emitting sources for exciting the phosphor. Each emitter is composed of an electron emitting portion, a pair of electrodes that apply voltage to the electron emitting portion, etc.
Further, a plate-shaped grid is located between the two plates. The grid is formed having a number of apertures that are aligned with the emitters. Spacers that maintain the gap between the plates are located on the grid. An electron beam that is emitted from each emitter is transmitted through its corresponding aperture of the grid and applied to a desired phosphor layer.
An SED described in U.S. Pat. No. 5,846,205 is known as a version that has a spacer assembly formed of a grid and spacers that resembles the ones described above. According to this SED, the plate-shaped grid has a number of spacer apertures, and columnar spacers that are a little smaller in diameter than the spacer apertures are passed through the spacer apertures, individually, and are fixedly bonded to the grid with an adhesive agent, frit, solder, or the like. Each spacer projects from both sides of the grid, and its opposite ends engage the respective inner surfaces of a faceplate and a rear plate, individually.
The manufacture of the spacer assembly is very troublesome, however, if it is done by passing the columnar spacers individually into a number of spacer apertures in the grid and fixing them with the adhesive agent or the like in the aforesaid manner, and it is hard to improve the manufacturing efficiency in this case. More specifically, each spacer is very small, having a diameter of hundreds of micrometers and a height of several millimeters, and its corresponding spacer aperture is also very small. Accurately inserting the very small spacers into the spacer apertures of the grid and fixedly bonding them to the grid with the adhesive agent or the like require high assembly accuracy and entail very hard operations. Further, the manufacturing cost is increased, and the manufacturing efficiency is lowered.
In order to reduce the movement of the electron beams, moreover, the spacers should be thinned, and the ratio between the diameter and height, that is, aspect ratio (height/diameter), should be heightened. It is hard, however, to manufacture spacers with high aspect ratios.